The thought of setting up personal (or even Debian-wide) Google+ servers
never occurred to me.

I think you might have missed the point. Google+ is a proprietary SaaS
used for selling your eyeballs to advertisers. It is unlikely that
Google will ever let it be installed on other servers, let alone
release the source code under a free license. Debian should avoid
using such SaaS offerings and promote the free alternatives that exist
and the movements that support them, some links:
http://autonomo.us/http://wiki.debian.org/FreedomBoxhttp://mako.cc/writing/hill-free_tools.html

Seriously, thats all fine stuff, but if having a hangout with 10+ people
on google+ helps Debian to get the bugs squashed, I can't see a reason
why we should not use it. It is much more pain free to use than any
other solution we have in Debian.

Two points, two cents each:

1. I see plenty of @gmail.com email addresses belonging to people in
Debian mailing lists. I guess they have that ad problem.
2. The "perfect storm" of people at such geographically distant
locations that a meetup anywhere isn't an option. Some will spend a lot
more on travel than others.